Laminated wood piece and door containing the same

ABSTRACT

A laminated wood piece is disclosed comprising a solid hardwood component having an upper surface and a lower surface that are substantially parallel to each other and a wood composite component having layers oriented substantially parallel to the lower surface of the solid hardwood component. The ratio of a thickness of the solid hardwood component to a thickness of the wood composite component being from about 1:1 to about 1:10. The laminated wood piece is suitable for use a door stile.

BACKGROUND OF THE INVENTION

[0001] Wood is a common material used to construct doors and otherarchitectural building elements. However, in recent years the cost ofsolid timber wood has increased dramatically as its supply shrinks dueto the gradual depletion of old-growth and virgin forests. It isparticularly expensive to manufacture doors from such material becausetypically less than half of harvested timber wood is converted tonatural solid wood lumber, the remainder being discarded as scrap.

[0002] Accordingly, because of both the cost of high-grade timber woodas well as a heightened emphasis on conserving natural resources,wood-based alternatives to natural solid wood lumber have been developedthat make more efficient use of harvested wood and reduce the amount ofwood discarded as scrap. Plywood, particle board and oriented strandboard (“OSB”) are examples of wood-based composite alternatives tonatural solid wood lumber that have replaced natural solid wood lumberin many structural applications in the last seventy-five years. Thesewood-based composites not only use the available supply of timber woodmore efficiently, but they can also be formed from lower-grade woodspecies, and even from wood wastes.

[0003] Wood composite materials are especially suitable formanufacturing doors, because their strength and insulation arecomparable or superior to natural solid wood lumber. However, becausethese composite materials consist of small particles (particle board),wood strands (OSB), flat pieces of low-grade wood species or somesimilar such material, products made from them do not have anattractive, grained appearance, but rather tend to have unsatisfactoryaesthetic finishes. This may make them unsuitable for use in doors,because generally it is preferred that doors have a pleasing aestheticfinish. However, wood composite materials can be used to form theinternal “core” of the door, and then top and bottom “doorskins” havinga wood or wood grain appearance are applied to the planar surfaces ofthe door to give it a satisfactory aesthetic finish.

[0004] Typically before these doorskins are applied to the internalcore, the core is “framed” with wood strips. The wood strips may areplaced adjacent to the top and bottom horizontal edge surfaces of thedoor (in which case they are known as “rails”) or they may be placedadjacent to the vertical edges of the door (and are then known as“stiles”). In addition to providing a pleasing aesthetic finish to thesides and edges to match the appearance of the aforementioned doorskins,the rails and stiles also enhance the structural integrity of the doorand help resist warpage. The stiles are also particularly importantbecause metal fixtures (such as the hinges that hold the door to thedoor frame, as well as the door lock) are installed in the door stileand held therein.

[0005] Preferably, each door stile would be manufactured from a singlepiece of solid hardwood, which would provide not only an attractivefinish, but provide excellent strength for holding the lock and hingefixtures. However, one-piece solid hardwood stiles are prohibitivelyexpensive for use in most all doors. Accordingly, laminated woodmaterials have been proposed as an alternative to one-piece solidhardwood stiles. These laminated wood composite styles are made bylaminating an outer hardwood strip to a “stile backer” made from a woodcomposite material. The outer hardwood strip provides a natural woodappearance, while the wood composite material provides screw holdingstrength, so that metal fixtures may be attached to the stile.

[0006] However, while these laminated composite stiles are considerablyless expensive than one-piece hardwood stiles they have poorscrew-holding strength and poor split resistance. The “screw-holding”strength is the amount of force required to pull a screw out of thestile, while the split resistance measures how well the wood resistssplitting when a nail or screw is inserted into it. These properties areimportant because they indicate whether the metal fixtures will be ableto withstand the forces, static and dynamic, exerted on and by a hungdoor.

[0007] For example, one commonly available laminated wood material isthe TIMBERSTRAND™ product from Trus Joist MacMillan, Inc., Boise, Id. Inthe TIMBERSTRAND™ wood composite material, the layers are arrangedperpendicular to the lower and upper surfaces of the solid hardwoodcomponent attached to wood composite material. Thus, the layers of thewood composite material are oriented perpendicular to the surface of thedoor stile (and thus parallel to the direction that the screw enters thewood composite material). Accordingly when a screw is inserted into thewood composite layers it has the effect of pushing the layers apart fromeach other, which not only reduces the screw holding strength of thelaminated wood door stile, but also reduces the split resistance.

[0008] Given the foregoing, there is a continuing need for a laminatedwood stile that not only has a pleasing surface finish and isinexpensive, but that also combines excellent screw holding strength andsplit resistance to allow for the installation of metal fixtures withinit.

BRIEF SUMMARY OF THE INVENTION

[0009] The invention provides a laminated wood piece comprising a solidhardwood component having an upper surface and a lower surface that aresubstantially parallel to each other and a wood composite componenthaving layers oriented substantially parallel to the lower surface ofthe solid hardwood component, the ratio of a thickness of the solidhardwood component to a thickness of the wood composite component beingfrom about 1:1 to about 1:10.

[0010] The invention also provides a door including a frame, the frameincluding at least one stile member, the at least one stile membercomprising a solid hardwood component having an upper surface and alower surface that are substantially parallel to each other; and a woodcomposite component having layers oriented substantially parallel to thelower surface of the solid hardwood component. The ratio of a thicknessof the solid hardwood component to a thickness of the wood compositecomponent is from 1:1 to 1:10, preferably from 1:1 to 1:5.

[0011] The invention also provides a method for manufacturing a doorcomprising the steps of providing a core, then providing a door stilecomprising a solid hardwood component having an upper surface and alower surface that are substantially parallel to each other, and a woodcomposite component having layers oriented substantially parallel to thelower surface of the solid hardwood component. This method furthercomprises the step of securing the door stile to the core, with the woodcomposite component contacting the core, and the solid hardwoodcomponent being on an outer side of the wood composite component.

[0012] The invention also provides a method for manufacturing a doorstile comprising the steps of preparing a wood composite panel havingseveral layers and a thickness of about 0.6 cm to about 6 cm, thencutting the wood composite panel into a plurality of wood compositesections, each wood composite section having a width of about 3 cm toabout 6 cm. Next, a solid hardwood component is provided having an uppersurface and a lower surface that are substantially parallel to eachother and one of the plurality of wood composite sections is attached tothe lower surface of the solid hardwood component, wherein the woodcomposite section has several layers oriented substantially parallel tothe lower surface of the solid hardwood component.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0013] The foregoing summary, as well as the following detaileddescription of preferred embodiments of the invention, will be betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the invention, there is shown in the drawingsembodiments which are presently preferred. It should be understood,however, that the invention is not limited to the precise arrangementsand instrumentalities shown in the drawings:

[0014]FIG. 1 is a perspective view of a laminated wood piece preparedaccording to the present invention;

[0015]FIG. 2 is a front view of the laminated wood piece shown in FIG.1;

[0016]FIG. 3 is a perspective view of a door incorporating a laminatedwood piece prepared according to the present invention;

[0017]FIG. 4 is a partial perspective view of a wood composite panelshowing the sections the panel is to be cut into according to thepresent invention; and

[0018]FIG. 5 is a perspective view of a prior art laminated wood piece.

DETAILED DESCRIPTION OF THE INVENTION

[0019] All parts, percentages and ratios used herein are expressed byweight unless otherwise specified. All documents cited herein areincorporated by reference.

[0020] As used herein, “wood” is intended to mean a cellular structure,having cell walls composed of cellulose and hemicellulose fibers bondedtogether by lignin polymer.

[0021] By “wood composite material” it is meant a composite materialthat comprises wood and one or more other additives, such as adhesivesor waxes. Non-limiting examples of wood composite materials includeoriented strand board (“OSB”), structural composite lumber (“SCL”),waferboard, particle board, chipboard, medium-density fiberboard,plywood, and boards that are a composite of strands and ply veneers. Asused herein, “flakes”, “strands”, and “wafers” are considered equivalentto one another and are used interchangeably. A nonexclusive descriptionof wood composite materials may be found in the Supplement Volume to theKirk-Rothmer Encyclopedia of Chemical Technology, pp 765-810, 6^(th)Edition.

[0022] The following describes preferred embodiments of the presentinvention, which provides an elongated laminated wood piece,particularly suitable for use as a stile in a composite door. Thislaminated wood piece includes a single piece of solid hardwood laminatedto layers of a wood composite component (e.g., strands, particles orveneers), these layers arranged substantially parallel to the lengthwisedirection of the piece, which, when compared to prior art laminatedwoods, increases the split resistance and screw-holding strength of thecomposite piece, provides maximum stiffness along the lengthwisedirection of the piece and minimizes the linear expansion in thisdirection. Laminated wood pieces prepared according to the presentinvention have a screw holding strength of about 400 lbs to about 1200lbs and a split resistance of greater than about 600 lbs to about 2500lbs, such as greater than about 1000 lbs, such as greater than 600 lbs.

[0023] The laminated wood piece may be installed as a stile in acomposite door so that the wood composite component faces inwardlytowards the center of the door, and the solid hardwood component is onthe outer side of the wood composite component to give the edge of thedoor a pleasing and attractive finish that preferably matches the woodgrain of the surface skin veneers.

[0024] As shown in FIG. 1, there is an elongated laminated woodcomposite piece 1 comprising a solid hardwood component 3 and a woodcomposite component 5. The solid hardwood component 3 has an uppersurface 14 and a lower surface 16, which are preferably substantiallyparallel to one another. The wood composite component 5 is laminated tothe lower surface 16 of the solid hardwood component 3. As can be seenin FIG. 1, the wood composite component 5 is composed of layers 9arranged substantially parallel to the upper surface of 14 and the lowersurface 16 of the wood composite piece 1. When the wood compositecomponent 5 is made from OSB, then at least about 90 wt %, such as atleast about 95 wt % of the strands in the OSB are oriented substantiallyparallel to the lengthwise (longitudinal) direction 24 of the piece 1.Arranging the layers in this parallel orientation provides maximumstiffness along the lengthwise (longitudinal) direction 24 of the piece1 and minimizes the linear expansion in this direction as well asprovides improved split-resistance and screw-holding strength.

[0025] The laminated wood pieces are made by laminating together thewood composite piece 5 to the solid hardwood piece 3. The solid hardwoodcomponent 3 is a single piece of solid hardwood which may be made fromwood species such as maple, oak, cherry, walnut. The wood compositematerial 5 is manufactured according to typical methods of manufacturingwood composite panels (not shown) and a section of this wood compositepanel is cut to attach to the solid hardwood component 3 to form thelaminated wood piece. (The width of this cut section itself determinesthe width of the laminated wood piece 1.) Either the top or bottomsurface of the section of the wood composite panel is placed in contactwith the solid hardwood component 3 and the components attached(preferably, adhesively bonded) together to form a laminated woodcomposite piece, which is suitable for use as a door stile. Methods ofattaching the wood composite material 5 to the solid hardwood component3 are discussed in greater detail below.

[0026] The laminated wood piece 1 may have a thickness, T, of about 0.9cm to about 6 cm, such as about 1.25 cm to about 6 cm, such as about 2.8cm to about 3.8 cm; and a width, W, of about 3 cm to about 6 cm, such asabout 3.5 cm to about 4.5 cm. 1.655 inches is the standard thickness fora door stile. The total door thickness is the sum of the stile thicknessplus the thickness of the veneer layers and crossbands, which aredescribed below. Individually, the thickness of the solid hardwoodcomponent is about 0.3 cm to about 1.3 cm, preferably about 0.6 cm toabout 1.1 cm, and the thickness of the wood composite component is about0.6 cm to about 5 cm, preferably about 2.2 cm to about 3.3 cm. The ratioof a thickness of the solid hardwood component to a thickness of thewood composite component is from about 1:1 to about 1:10, such as fromabout 1:2 to about 1:5.

[0027] As is shown in FIG. 2, the layers 9 of the wood compositecomponent 5 are arranged to be substantially parallel to the uppersurface and lower surface of the solid hardwood component 3. A screw 11(or nail or similar fastening device suitable to attach metal fixturesto a door stile) is inserted into the piece 1, travels through the solidhardwood component 3, and then enters in a perpendicular direction tothe layers 9 of the wood composite component 5. The screw 11 is heldfirmly in place by the solid hardwood component 3 and the dense layers 9of the wood composite component 5. The internal bonding strength of thedense wood composite component 5 cooperates with the good bondingstrength provided by the solid hardwood component 3 so that the woodcomposite piece 1 has excellent screw holding and split resistanceproperties.

[0028] Preferably, the wood composite component 5 is made from OSBmaterial, the strands being oriented substantially parallel to the lowersurface 16 of the solid hardwood component 3. Preferably, at least about90 wt %, such as at least about 95 wt % of the strands in the OSB areoriented substantially parallel to the lengthwise (longitudinal)direction 24 of the piece 1. This orientation provides maximum stiffnessand minimizes linear expansion in the lengthwise direction as well asenhancing the strength properties of the laminated wood piece 1.

[0029] The oriented strand board is derived from a starting materialthat is naturally occurring hard or soft woods, singularly or mixed,whether such wood is dry (having a moisture content of between 2 wt %and 12 wt %) or green (having a moisture content of between 30 wt % and200 wt %). Typically, the raw wood starting materials, either virgin orreclaimed, are cut into strands, wafers or flakes of desired size andshape, which are well known to one of ordinary skill in the art.

[0030] After the strands are cut they are dried in an oven and thencoated with a special formulation of one or more polymeric thermosettingbinder resins, waxes and other additives. The binder resin and the othervarious additives that are applied to the wood materials are referred toherein as a coating, even though the binder and additives may be in theform of small particles, such as atomized particles or solid particles,which do not form a continuous coating upon the wood material.Conventionally, the binder, wax and any other additives are applied tothe wood materials by one or more spraying, blending or mixingtechniques, a preferred technique is to spray the wax, resin and otheradditives upon the wood strands as the strands are tumbled in a drumblender.

[0031] After being coated and treated with the desired coating andtreatment chemicals, these coated strands are used to form amulti-layered mat. The coated wood materials (in the form of strands)are spread on a conveyor belt with the top and bottom exterior layersbeing the surface layer and one or more interior “core” layers. The woodstrands are positioned on the conveyor belt oriented substantiallyparallel to the lower surface 16 of the solid hardwood component 3, andpreferably, at least about 90 wt %, such as at least about 95 wt % ofthe strands in the OSB are oriented substantially parallel to the lowersurface 16 of the solid hardwood component 3.

[0032] Various polymeric resins, preferably thermosetting resins, may beemployed as binders for the wood flakes or strands. Suitable polymericbinders include isocyanate resin, urea-formaldehyde, phenolformaldehyde, melamine formaldehyde (“MUF”) and the copolymers thereof.Isocyanates are the preferred binders, and preferably the isocyanatesare selected from the diphenylmethane-p,p′-diisocyanate group ofpolymers, which have NCO-functional groups that can react with otherorganic groups to form polymer groups such as polyurea, —NCON—, andpolyurethane, —NCOON—. 4,4-diphenyl-methane diisocyanate (“MDI”) ispreferred. A suitable commercial MDI product is Rubinate pMDI availablefrom ICI Chemicals Polyurethane Group. Suitable commercial MUF bindersare the LS 2358 and LS 2250 products from the Dynea corporation.

[0033] The binder concentration is preferably in the range of about 3 wt% to about 8 wt %. A wax additive is commonly employed to enhance theresistance of the OSB panels to moisture penetration. Preferred waxesare slack wax or an emulsion wax. The wax loading level is preferably inthe range of about 1 wt % to about 3.0 wt % (based on the weight ofsolids).

[0034] After the multi-layered mats are formed according to the processdiscussed above, they are compressed under a hot press machine thatfuses and binds together the wood materials, binder, and other additivesto form consolidated OSB panels of various thickness and sizes. The hightemperature also acts to cure the binder material. Preferably, thepanels of the invention are pressed for 2-15 minutes at a temperature ofabout 175° C. to about 240° C. The resulting composite panels will havea density in the range of about 35 lbs/ft³ to about 48 lbs/ft³ (asmeasured by ASTM standard D1037-98). The density ranges from 40 lbs/ft³to 48 lbs/ft³ for southern pine, and 35 lbs lbs/ft³ to 42 lbs/ft³ forAspen. The thickness T′ of the OSB panels, as shown in FIG. 4, will befrom about 0.6 cm (about ¼″) to about 5 cm (about 2″), such as about1.25 cm to about 6 cm, such as about 2.8 cm to about 3.8 cm.

[0035] After being compressed in the hot press machine, the moisturecontent of the panels should be between about 6 wt % to about 8 wt %,which matches the moisture content of the solid hardwood component thatthe OSB is laminated to in forming the stile. If the moisture content ofthe OSB does not match that of the solid hardwood, then the laminatedwood piece is liable to bow during use on account of the linearexpansion of the OSB. The OSB panel was then cut into sections, as shownin FIG. 4, with the width W′ of each section being exactly identical tothe width of the stiles 1 and 13, and correspondingly the width of therails 12 and 14. Thus, the width of the sections were about 3 cm toabout 6 cm, such as about 3.5 cm to about 4.5 cm.

[0036] The wood composite component 5 (e.g., the OSB panel madeaccording to the aforementioned procedure) and the solid hardwoodcomponent 3 are then attached to each other to form a wood compositestile 1, such as by adhesively bonding them together. Common woodadhesives, such as polyvinyl alcohol (“PVA”) is applied to each of thecomponents and the components brought into contact with each other toform an adhesive bond. The components may then be clamped and heldtogether for several hours to promote the establishment of a goodadhesive bond. If desired, an RF laminating apparatus may be used. Thisapparatus has a RF heating plate that emanates a RF high frequencyelectric field, which heats and cures the adhesive.

[0037] In operation, an adhesive is applied to the lower surface 14 ofthe solid hardwood component 3 or one of the surface layers of the woodcomposite component 5, and then the components are brought into contactwith each other to from a laminated wood piece 1. Then the laminatedwood piece 1 was arranged on a conveyor and introduced into the RFlaminating apparatus in such a way that the surfaces to which the gluewas applied were oriented perpendicular to the plane of the RF heatingplate. Lateral pressure was applied to the laminated wood piece 1 toassure good contact between the wood composite component 5 or the solidhardwood component 3 while they are under RF heating. The curing time(or the amount of time that the laminated wood piece 1 is exposed to theRF high frequency electric field) should be between 1 to 3 minutes,depending on type of equipment, type of glue and amount of RF power.

[0038] As shown in FIG. 3, the wood composite piece 1 may beincorporated as a stile member in the frame of a composite door 15. By“stile member” it is meant that the wood composite piece forms the partof the frame that is placed adjacent to the vertical edge of the door,the stile member need not run the entire vertical length of the door.The composite door 15 in FIG. 3 includes a rectangular wood frame formedby door stiles 11 and 13 (which run along the vertical edge of the door15), a top rail 14 and a bottom rail 12, all of which have the samecross section. In the preferred embodiment, the stiles 11 and 13 run thefull length of the frame and overlie and abut the ends of the rails 12and 14. The two stiles have a length of about 120 cm to about 305 cm,preferably about 215 cm to about 245 cm. The width and thickness of thestiles are the same as set forth above for the laminated wood piece.

[0039] Preferably, the space enclosed by the frame 19 is substantiallyfilled with a core 20, although the space can instead be relativelyempty or contain a Z-type member or the like. The core 20 can be a solidhardwood or a wood composite material, or made from various types ofthermoplastic or thermosetting materials, compressed mineral board,organic or inorganic fillers, or honey-comb structures, as well as anyother suitable core-forming material. Particularly preferred arepolymeric foam materials or wood composites like particleboard. As shownin FIG. 3, the stiles 11, 13 are positioned adjacent to the core 20,with the wood composite component 5 in contact with the core 20, and thesolid hardwood component 3 located on the outer side of the woodcomposite 5.

[0040] The entire frame and core is covered on each side by a doorskin22. A crossband 14 may be used between the core and hardwood doorskin toprevent telegraphing (when the texture of the core shows through theveneer). This crossband 14 is typically made of low density hardwoodveneer or high density fiberboard with a thickness of at least {fraction(1/16)} inch. Each doorskin may be made from many different types ofmaterials including wood veneers made from different species of solidwoods and different types of wood composites. Also suitable arecompression molded resins incorporating reinforcing fibers, as well asmoldings made through resin transfer molding, vacuum assisted resinintrusion, rotational molding, low and high pressure injection molding.For architectural doors, suitable doorskin materials include hardwoodveneers, and high pressure decorative laminate (HPDL) door faces.Regardless of the material used, it is generally preferred that thedoorskins 22 have an appearance simulating a wood grain. When finallyassembled, the sum of the thickness of the surface skins 22 and the woodframe 19 should approximate the thickness of the door frame in which thedoor is to be installed.

[0041] The assembly of the rails, stile and core to form a compositedoor is preferably carried out on a flat table to facilitate the evenregistration of the frame elements with respect to each other and to thecore. Preferably adhesive bonding is used and common wood adhesives,such as PVA, are acceptable. The attachment between adjoining members ofthe frame as well as between the core and frame can be made byadhesives, staples, nails, screws or any other fastening technologiesknown to those of ordinary skill in the art. The elements of the framemay be attached or secured to each other and then the assembled frameattached to the core, or the elements of the frame may be individuallyattached and assembled directly onto the core 20 of the door.Alternatively, when the core 20 is made from a foam material, the frame19 may be assembled first, and the foam material then supplied (orpoured) in liquid form into the frame 19 to form the core 20.

EXAMPLE I

[0042] Split resistance and screw holding tests were carried out with alaminated wood composite piece composed of an OSB wood compositecomponent cut from an OSB panel and laminated to a solid maple hardwoodcomponent.

[0043] The OSB panels were formed as follows. The wood strands wereblended in a drum blender with the 1 wt % to 3 wt % wax and 3 wt % to 8wt % MDI polymeric binder for approximately 2 minutes. The strands werethen deposited on a conveyor belt to form a mat and the mat was thenhot-pressed to form an OSB panel. Hot press conditions were as follows:(1) press closing time: 40 seconds, (2) press cooking time: 260 seconds,(3) de-gas time: 20 seconds, (4) press control temperature: 225° C.(430° F.). The OSB panel thereby produced has a density of 44.6 lbs/ft³,a thickness of 0.945 inches, and a final moisture content of 5.9 wt % to6.4 wt %. After being sanded on both sides, the final thickness of thepanel was 0.875 inches.

[0044] A section having a width of 1.655 inches was cut from the OSBpanel and laminated to the solid hardwood maple piece to form a woodcomposite piece prepared according to the present invention. The sectionfrom the OSB panel and the solid hardwood maple piece were attached toeach other in the following fashion: the PVA glue was applied to the OSBpiece, and the maple hardwood piece and OSB piece clamped together toassure good contact. The pieces remained clamped for at least 4 hours,and after release, the assemblies were conditioned at room temperaturefor at least 48 hours before testing. The final thickness of thelaminated wood piece thus formed was 1.25 inches.

[0045] This section of the wood composite piece was then compared with asection of a prior art product, viz. Trus Joint MacMillan'sTIMBERSTRAND™ product, which is solid maple hardwood laminated to apiece of oriented strand board made from aspen wood strands. As can beseen in FIG. 5, in the TIMBERSTRAND™ product 32, unlike the laminatedwood pieces prepared according to the present invention, the layers 44of the wood composite component 46 (which is in this case OSB) arearranged perpendicular to the lower surface 41 and upper surface 39 ofthe solid hardwood component 35.

[0046] The Split resistance of these laminated wood pieces was testedaccording to the protocol laid out in National Wood Windows and DoorAssociation (“NWWDA”) standard TM-5-1990. The laminated wood piece asprepared above was cut into a three inch long specimen, and a sufficientof the wood composite material trimmed off the piece so that the overallthickness of this specimen was one inch. The specimen was conditioned tobe at an equilibrium moisture content of 75° F.±10° F. and 50%±5%relative humidity. Next 0.134 inches (plus or minus 0.005 inches) wascut away from the upper surface 14 of the solid hardwood component 3 (tosimulate the removal of material in preparing to attach a hinge leaf tothe laminated wood piece). Then a one-half inch diameter hole wasdrilled through the specimen, the hole being centered on the diagonalintersection of two lines, each of which connect opposite corners of theupper surface 14 of the solid hardwood component 3.

[0047] The apparatus used to conduct the test was an Instron hydraulictesting machine having a moveable crosshead to apply a tensile load viaa split dowel road to the testing specimens. The specimen was mountedwith the split dowel rod inserted in the one-half inch hole describedabove. The specimen was oriented with the three inch lengthperpendicular to the direction of the load (applied in tension), and theload then applied continuously at a rate of motion of the moveablecrosshead of 0.1 inches (2.5 mm) per minute. The maximum load that canbe applied before the specimen begins to split is the split resistanceof the section. This test was repeated with an additional 15 specimens,and the results averaged.

[0048] The split resistance for the laminated wood pieces preparedaccording to the present invention was in excess of 1200 lbs, the exactmeasurement is not known because at a 1200 lbs load the laminated woodpiece had not broken, but the test had to be discontinued for safetyreasons. By contrast, the TIMBERSTRAND™ product had a significantlysmaller split resistance of 311 lbs.

[0049] The screw-holding capacity was tested according to the protocollaid out in National Wood Windows and Door Association (“NWWDA”)standard TM-10. As in the split resistance test described above, a threeinch specimen of the laminated wood piece was cut, and a sufficient ofthe wood composite material trimmed off the piece so that the overallthickness of this specimen was one inch. The specimen was conditioned tobe at an equilibrium moisture content at 75° F.±10° F. and 50%±5%relative humidity. Next 0.134 inches (plus or minus 0.005 inches) wascut away from the upper surface 14 of the solid hardwood component 3. A⅛ inch drill bit was used to drill a hole in the specimen, and a 2 inchlong #10 screw inserted into the hole. The root diameter was about 0.138inches.

[0050] The plate was then positioned on top of the specimen and thescrew inserted through the plate hole and into the lead hole deep enoughto engage one inch of the constant diameter portion of the threads,being careful to insert the screw with a turning motion so as not toreduce the thread engagement strength of the specimen. The specimen wasthen inserted into the load applying holding attachment of the hydraulictensioning apparatus with the screw head up, and the screw head engagedby the holding attachment. A tensile load applied continuously at a rateof motion of the moveable crosshead of 0.1 inches (2.5 mm) per minute.

[0051] The screw withdrawal capacity for the laminated wood piecesprepared according to the present invention was 936 lbs for the OSBcomposite material itself (without the hardwood) and 1035 lbs for thewood composite piece overall (with the hardwood). By contrast, theTIMBERSTRAND™ product had a screw withdrawal capacity of 708 lbs(without the hardwood layer) and 1017 lbs for the wood composite pieceoverall (with the hardwood). Thus, the laminated wood piece preparedaccording to the present invention has significantly higher screwwithdrawal performance than the prior art.

[0052] This data demonstrates that laminated wood composite pieces inwhich the wood composite layers are oriented parallel to the lowersurface of the solid hardwood component (and thus, the layers areperpendicular to the direction at which the screw enters the woodcomposite layers) has a split resistance and screw holding capacity thatare significantly better than prior art laminated wood composite piecesin which the wood composite layers are perpendicular to the lowersurface of the solid hardwood component (and thus, parallel to thedirection that the screw enters). Such results would be unexpected byone of ordinary skill in the art.

[0053] It will be appreciated by those skilled in the art that changescould be made to the embodiments described above without departing fromthe broad inventive concept thereof. It is understood, therefore, thatthis invention is not limited to the particular embodiments disclosed,but it is intended to cover modifications within the spirit and scope ofthe present invention as defined by the appended claims.

We claim:
 1. A laminated wood piece comprising: (a) a solid hardwood component having an upper surface and a lower surface that are substantially parallel to each other; and (b) a wood composite component having layers oriented substantially parallel to the lower surface of the solid hardwood component; wherein the ratio of a thickness of the solid hardwood component to a thickness of the wood composite component is from about 1:1 to about 1:10, preferably from about 1:2 to about 1:5.
 2. The laminated wood piece according to claim 1, wherein the thickness of the solid hardwood component is about 0.3 cm to about 1.3 cm, preferably about 0.6 cm to about 1.1 cm, and the thickness of the wood composite component is about 0.6 cm to about 5 cm, preferably about 2.2 cm to about 3.3 cm.
 3. The laminated wood piece according to claim 1, wherein the wood composite component is an oriented strand board.
 4. The laminated wood piece according to claim 3, wherein a width of the piece is about 3 cm to about 6 cm, preferably about 3.5 cm to about 4.5 cm, and a length of the piece is about 120 cm to about 305 cm, preferably about 215 cm to about 245 cm.
 5. The laminated wood piece according to claim 1, wherein the laminated wood piece has a screw holding strength of about 400 lbs to about 1200 lbs.
 6. The laminated wood piece according to claim 1, wherein the wood composite component is an oriented strand board and has a density of about 35 lbs/ft² to about 48 lbs/ft², preferably about 38 lbs/ft² to about 44 lbs/ft².
 7. The laminated wood piece according to claim 1, wherein the laminated wood piece has a split resistance of greater than about 1000 lbs.
 8. The laminated wood piece according to claim 1, wherein the wood composite component is an oriented strand board comprising strands, in which at least 90 wt % of the strands are oriented substantially parallel to the length of the laminated wood piece.
 9. The laminated wood piece according to claim 1, wherein the wood composite component is an oriented strand board containing from about 3 wt % to about 6 wt % of binder, and from about 1% to about 2.5% of a wax additive.
 10. A door including a frame, the frame including at least one stile member, the stile member comprising: (a) a solid hardwood component having an upper surface and a lower surface that are substantially parallel to each other; and (b) a wood composite component having layers oriented substantially parallel to the upper surface of the solid hardwood component; wherein the ratio of a thickness of the solid hardwood component to a thickness of the wood composite component is from about 1:1 to about 1:10, preferably from about 1:2 to about 1:5.
 11. The door according to claim 10, wherein the door further comprises an additional stile member being arranged substantially parallel to the at least one stile member and both the at least one stile member and the additional stile member have a substantially vertical orientation.
 12. The door according to claim 10, wherein the door further includes a core, a pair of rails, and a pair of opposed doorskins.
 13. The door according to claim 12, wherein the wood composite component of the at least one stile is in contact with the core.
 14. A method for manufacturing a door comprising the steps of: providing a core; providing a door stile comprising: (a) a solid hardwood component having an upper surface and a lower surface that are substantially parallel to each other; and (b) a wood composite component attached to the solid hardwood component, the wood composite component having layers oriented substantially parallel to the lower surface of the solid hardwood component; and securing the door stile to the core, with the wood composite component contacting the core, and the solid hardwood component being on the outer side of the wood composite component.
 15. A method for manufacturing a door stile comprising the steps of: preparing a wood composite panel having several layers and a thickness of about 0.6 cm to about 6 cm; cutting the wood composite panel into a plurality of wood composite sections, each wood composite section having a width of about 3 cm to about 6 cm; providing a solid hardwood component having an upper surface and a lower surface that are substantially parallel to each other; and attaching one of the plurality of wood composite sections to the lower surface of the solid hardwood component, wherein the wood composite section has several layers oriented substantially parallel to the lower surface of the solid hardwood component.
 16. The method according to claim 15, wherein the solid hardwood component has the same width as each of the wood composite sections. 